1. Field of the Invention
This invention relates to a clamping device for regulating fluid flow through flexible tubing and, more particularly, to a clamping device for use in intravenous parenteral fluid administration sets.
2. Description of the Prior Art
Many clamps have been developed for controlling the rate of flow of parenteral fluid administered to a patient through the plastic tubing which is used for transporting parenteral fluid from the solution container to the patient. However, these clamps have not proved as reliable and accurate in use as desired, particularly with respect to regulating and maintaining uniform flow rates.
Most clamps are designed to flatten tubing so that the walls of the tubing are more or less parallel producing a long flat oval-shaped lumen. The rate of flow of fluid through tubing compressed in this manner is difficult to control precisely. Moreover, there is considerable strain imposed on the plastic by clamps of this type. Under such strain, most plastics undergo "cold flow" to relieve the strain causing the tubing to flatten still further and collapse inwardly thus decreasing the fluid flow rates. As a result, the nurse or attendant must frequently readjust the clamp to maintain relatively constant fluid flow.
A few clamps have been developed which do not flatten the tube uniformly as shown, for example, in U.S. Pat. No. 3,685,787. This clamp consists of a base having a tapered V-shaped groove into which plastic tubing is progressively compressed by a roller in such a manner that there is essentially no space for the plastic to "cold flow" into since the peripheral surfaces of the tubing are confined.
Another attempt to solve the problem of controlling fluid flow in intravenous tubing is described in U.S. Pat. No. 3,802,463. With this device, opposed walls of the tubing are variably compressed to modify the size of a pair of lumens formed along the outer edges of the compressed tubing. Central portions of the opposite walls are brought together in gradually increasing interior surface contact so that the lumens in the uncompressed outer edges gradually decrease in size until flow of fluid through the tubing ceases.
Another problem associated with most clamps is the so-called "abusive tug" problem. The tubing used in intravenous sets for administering parenteral solutions is typically made of soft polyvinyl chloride. When the tubing is intentionally or accidentally given a strong tug, the tubing stretches. When the abusive tug is released, a large increase in flow rate occurs. An example of a clamp designed to avoid the effects of an abusive tug is U.S. Pat. No. 4,047,694. In this clamp, the side portions of the tubing wall are permitted to migrate into recesses formed between undercut shoulder portions of the roller or wheel and the sides of the clamp housing.